First, in case of mounting semiconductor elements such as IC chips and the like on printed wiring board, first, solder bumps are formed for semiconductor element mounting pads (hereinafter, merely referred to as “conductor pad”) formed on the printed wiring board. A part of the conductor pad is covered with a solder resist layer, and the center portion of the conductor pad is only exposed. In order to form a solder bump for such conductor pad, first, the printed wiring board is set in a solder paste printer, then a solder printing mask such as metal mask, plastic mask and the like (provided with an opening for printing corresponding to the conductor pad formed in the printed wiring board) is laminated on the printed wiring board, and alignment of an alignment mark formed in the printed wiring board and an alignment mark of the mask for printing is carried out.
And, after printing solder paste on the conductor pad and removing the mask for printing from the printed wiring board, a solder bump is formed on the conductor pad by carrying out a reflow treatment by setting the printed wiring board on a reflow device (refer to as Japanese unexamined patent publication No. H11-40908).